Publications by authors named "Ludivine Challet Meylan"

4 Publications

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ZNRF3 and RNF43 cooperate to safeguard metabolic liver zonation and hepatocyte proliferation.

Cell Stem Cell 2021 Jun 11. Epub 2021 Jun 11.

Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland. Electronic address:

AXIN2 and LGR5 mark intestinal stem cells (ISCs) that require WNT/β-Catenin signaling for constant homeostatic proliferation. In contrast, AXIN2/LGR5+ pericentral hepatocytes show low proliferation rates despite a WNT/β-Catenin activity gradient required for metabolic liver zonation. The mechanisms restricting proliferation in AXIN2+ hepatocytes and metabolic gene expression in AXIN2+ ISCs remained elusive. We now show that restricted chromatin accessibility in ISCs prevents the expression of β-Catenin-regulated metabolic enzymes, whereas fine-tuning of WNT/β-Catenin activity by ZNRF3 and RNF43 restricts proliferation in chromatin-permissive AXIN2+ hepatocytes, while preserving metabolic function. ZNRF3 deletion promotes hepatocyte proliferation, which in turn becomes limited by RNF43 upregulation. Concomitant deletion of RNF43 in ZNRF3 mutant mice results in metabolic reprogramming of periportal hepatocytes and induces clonal expansion in a subset of hepatocytes, ultimately promoting liver tumors. Together, ZNRF3 and RNF43 cooperate to safeguard liver homeostasis by spatially and temporally restricting WNT/β-Catenin activity, balancing metabolic function and hepatocyte proliferation.
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http://dx.doi.org/10.1016/j.stem.2021.05.013DOI Listing
June 2021

Phenotypic landscape of intestinal organoid regeneration.

Nature 2020 10 7;586(7828):275-280. Epub 2020 Oct 7.

Friedrich Miescher Institute for Biomedical Research (FMI), Basel, Switzerland.

The development of intestinal organoids from single adult intestinal stem cells in vitro recapitulates the regenerative capacity of the intestinal epithelium. Here we unravel the mechanisms that orchestrate both organoid formation and the regeneration of intestinal tissue, using an image-based screen to assay an annotated library of compounds. We generate multivariate feature profiles for hundreds of thousands of organoids to quantitatively describe their phenotypic landscape. We then use these phenotypic fingerprints to infer regulatory genetic interactions, establishing a new approach to the mapping of genetic interactions in an emergent system. This allows us to identify genes that regulate cell-fate transitions and maintain the balance between regeneration and homeostasis, unravelling previously unknown roles for several pathways, among them retinoic acid signalling. We then characterize a crucial role for retinoic acid nuclear receptors in controlling exit from the regenerative state and driving enterocyte differentiation. By combining quantitative imaging with RNA sequencing, we show the role of endogenous retinoic acid metabolism in initiating transcriptional programs that guide the cell-fate transitions of intestinal epithelium, and we identify an inhibitor of the retinoid X receptor that improves intestinal regeneration in vivo.
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http://dx.doi.org/10.1038/s41586-020-2776-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7116869PMC
October 2020

Self-organization and symmetry breaking in intestinal organoid development.

Nature 2019 05 24;569(7754):66-72. Epub 2019 Apr 24.

Friedrich Miescher Institute for Biomedical Research (FMI), Basel, Switzerland.

Intestinal organoids are complex three-dimensional structures that mimic the cell-type composition and tissue organization of the intestine by recapitulating the self-organizing ability of cell populations derived from a single intestinal stem cell. Crucial in this process is a first symmetry-breaking event, in which only a fraction of identical cells in a symmetrical sphere differentiate into Paneth cells, which generate the stem-cell niche and lead to asymmetric structures such as the crypts and villi. Here we combine single-cell quantitative genomic and imaging approaches to characterize the development of intestinal organoids from single cells. We show that their development follows a regeneration process that is driven by transient activation of the transcriptional regulator YAP1. Cell-to-cell variability in YAP1, emerging in symmetrical spheres, initiates Notch and DLL1 activation, and drives the symmetry-breaking event and formation of the first Paneth cell. Our findings reveal how single cells exposed to a uniform growth-promoting environment have the intrinsic ability to generate emergent, self-organized behaviour that results in the formation of complex multicellular asymmetric structures.
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http://dx.doi.org/10.1038/s41586-019-1146-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6544541PMC
May 2019

Generation of vascular endothelial and smooth muscle cells from human pluripotent stem cells.

Nat Cell Biol 2015 Aug 27;17(8):994-1003. Epub 2015 Jul 27.

1] Department of Stem Cell and Regenerative Biology and Harvard Stem Cell Institute, Harvard University, Massachusetts 02138, USA [2] Cardiovascular Research Center and Cardiology Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA [3] Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital and Dana Farber Cancer Institute, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.

The use of human pluripotent stem cells for in vitro disease modelling and clinical applications requires protocols that convert these cells into relevant adult cell types. Here, we report the rapid and efficient differentiation of human pluripotent stem cells into vascular endothelial and smooth muscle cells. We found that GSK3 inhibition and BMP4 treatment rapidly committed pluripotent cells to a mesodermal fate and subsequent exposure to VEGF-A or PDGF-BB resulted in the differentiation of either endothelial or vascular smooth muscle cells, respectively. Both protocols produced mature cells with efficiencies exceeding 80% within six days. On purification to 99% via surface markers, endothelial cells maintained their identity, as assessed by marker gene expression, and showed relevant in vitro and in vivo functionality. Global transcriptional and metabolomic analyses confirmed that the cells closely resembled their in vivo counterparts. Our results suggest that these cells could be used to faithfully model human disease.
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http://dx.doi.org/10.1038/ncb3205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4566857PMC
August 2015